Sealing ring for a dry running piston rod

ABSTRACT

A sealing ring, in particular for a piston rod with a circular cross-section, which has a height in the axial direction as well as a surface oriented towards a sliding surface, with the surface being executed to extend cylindrically over a part of the height in order to form a sealing surface and being executed to become wider along a further part. The sealing ring has a high sealing action in the axial direction so that a majority of the gas flows out between the piston rod and the sealing surface so that a gas storage arises.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to a sealing ring for a dry running piston rod.

2. Description of the Prior Art

Sealing rings are usually arranged pairwise one behind the other inseries and form in this manner a so-called packing. The pressuredifference acting on the individual sealing rings causes their sealingsurfaces to be pressed onto the sliding surfaces of the body to besealed, for instance, a piston rod. Such sealing rings are known, forexample, from the patent CH 439 897. These known sealing rings have thedisadvantage that the sealing surfaces pressed against the slidingsurface cause a strong heat of friction, which leads to overheating andrapid wear. This is true, in particular, for the use of sealing rings indry running piston compressors which manage in the compression partwithout any foreign lubrication. Compressors of this type have fixedsealing rings past which a piston rod is moved.

SUMMARY OF THE INVENTION

The object of the present invention is to propose a sealing ringsuitable for dry running apparatuses and having an improved sealingbehavior.

The sealing ring in accordance with the invention has a height H in theaxial direction as well as a surface oriented towards the dry runningsliding surface of the body to be sealed off, which is executed in sucha manner that it extends parallel to the sliding surface over a portionof the height H and thus forms a sealing surface. The remaining portionof the height H of the sealing ring is spaced from the sliding surface.

In an advantageous embodiment of the sealing ring in accordance with theinvention, the remaining portion of the height H of the sealing ring,which does not lie in contact with the sliding surface, is madeconically divergent.

The sealing ring is to be arranged in a dry running piston compressor,in particular, with respect to the piston rid in such a manner that theconically divergent region is oriented towards the cylinder space anddiverges in the direction towards the cylinder space. A sealing ring ofthis type has the advantage that the sealing surface of the sealing ringlying in contact with the piston rod is relatively small, which resultsin reduced friction. A further advantage of the embodiment of thesurface in accordance with the invention is to be seen in the fact thatthrough its shape in combination with the reduced sealing surface thegas attempts to flow between the sealing surface and the piston rid sothat a gas bearing arises between the sealing surface and the pistonrod. Such a gas bearing has the advantage that the friction between thepiston rod and the sealing surface is further reduced.

A sealing ring of this kind in accordance with the invention can, inparticular, be advantageously used when the fixed seal elements have ahigh sealing action in the axial direction so that a gas bearing arises,because a large part of the gas flows out between the piston rod and thesealing surface.

The design of the surface oriented towards the sliding surface in theaxial direction can be realized in a number of embodiments in such amanner that the surface of a first partial region has a surfaceextending parallel to the sliding surface and a second partial regionhas a surface spaced from the sliding surface.

The sealing ring in accordance with the invention is suitable, inparticular, for sealing dry running piston compressors operating undervery high pressure.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1a is a plan view of a ring-shaped seal part;

FIG. 1b is a side view of the seal part of FIG. 1a;

FIG. 1c is a plan view of a closure part;

FIG. 1d is a side view of the closure part of FIG. 1c;

FIG. 1e is a plan view of an assembled sealing ring;

FIG. 1f is a side view of the assembled sealing ring of FIG. 1e;

FIG. 1g is a section through the seal part of FIG. 1a along the lineA—A;

FIG. 2 is a perspective view of a further embodiment of a sealing ring;

FIG. 3 is a longitudinal section through a dry running sealingarrangement;

FIG. 4 is a plan view of the sealing ring of FIG. 2;

FIG. 4a is a cross-section through the sealing ring along the line(B—B);

FIG. 4b is a further cross-section through the sealing ring along theline (C—C);

FIG. 4c is a side view of the sealing ring from the direction (E).

DETAILED DESCRIPTION OF THE PREFERRED EXEMPLARY EMBODIMENTS

FIG. 1a shows a ring-shaped seal part 2 which has a sector-like cut-out3 so that the seal part 2 has an opening at this position. The seal part2 has a sealing surface 2 a which is oriented towards the piston rod.FIG. 1g shows a section along the line A—A and shows the L-shapedcross-section which the seal part 2 has in the present embodiment. Thesurface 2 a has a height H, with a part 2 b of the surface 2 a being ofcylindrical shape, contacting the piston rod 4, which is shown as abroken line, and forming a contact surface 2 b. The contact surface 2 bis at least 1 mm thick in the axial direction. A further part 2 c of thesurface 2 a diverges conically from the surface of the piston rod 4. Thegas (G) flowing up from the side of the cylinder enters between theconically diverging surface 2 c and the piston rod 4 and flows onthrough between the contact surface 2 b and the piston rod 4. In thismanner, a gas bearing arises between these two surfaces, whichsubstantially reduces the friction.

The entire sealing ring 12 has an elastic behavior and is advantageouslysurrounded by a hose spring 13 lying in the groove 1 a, so that thesealing ring 12 lies under an elastic biasing stress against the pistonrod 4. The gas flowing through between the contact surface 2 b and thepiston rod 4 exerts a force opposite to the action of the hose spring.The gas flowing through between the contact surface 2 b and the pistonrod 4 thus effects a reduction of the force pressing the sealing elementagainst the piston rod 4.

The seal part 2 has a main part 2 e which runs out at both ends into endparts 2 d. From the side view of FIG. 1b, it is evident that the two endparts 2 d are made thinner in the direction of a normal S to the planespanned by the seal part 2, or in the direction of motion of the pistonrod 4, than the main part 2 e. FIG. 1c shows a closure part 1 which hasa main part le as well as end parts 1 g which adjoin it at both ends andare of ring shape. FIG. 1d shows a side view of the illustration in FIG.1c of the closure part 1, with the closure part having a groove 1 a inthe peripheral direction for receiving a hose spring 13. Both the sealpart 2 and also the closure part 1 have resilient properties. FIG. 1eshows a sealing ring 12 assembled from the closure part 1 and the sealpart 2. In the process, the closure part 1 is placed onto the seal part2 in such a manner that the closure part 1 lies on the lower part 2 f ofthe seal part 2 and that the closure part 1 surrounds the upper part 2 eof the seal part 2 in the form of a ring. The main part 1 e covers thecut-out 3 of the seal part 2 and lies in contact with the end parts 2 din the direction of the normal S. The main part 1 e can have a profileas shown in FIG. 1g on the surface facing the piston rod 4. The sealingring 12 thereby has a seal function over the entire jacket surface ofthe piston rod 4. The main part 1 e as well as the seal part 2 have aclearance S1 in the peripheral direction of the seal part 2. The sealingring 12 is advantageously surrounded by a hose spring 13 so that thesealing ring disk stands under prestress. During the use of the sealingring 12 as a seal element, the 15 movement of the piston rod leads towear of the sealing surface 2 a, which results in the removal ofmaterial. The hose spring 13, the clearance S1, as well as the resilientproperties of the sealing ring disk ensure that the sealing surface 2 acan continue to lie in contact with the surface of the piston rod 4.FIG. 1f shows a side view of the sealing ring 12 of FIG. 1e.

FIG. 2 shows an exploded view of a further sealing ring 12 consisting ofa sealing part 2, a cover ring 1 which can be placed over it in theperipheral direction of the sealing ring 2, as well as a hose spring 13surrounding the cover ring 1 in the peripheral direction. The cover ring1 seals off the ring gap 2 l in the radial as well as in the axialdirection.

The plan view of the sealing ring 2 shown in FIG. 4 has a surface 2 a, 2b which extends circularly along the inner circle and faces the pistonrod 4 and performs a sealing function. The sealing part 2 is executed asa single piece ring with a parting joint 2 l so that the sealing part 2runs out into two ends 2 h, 2 k. The end 2 k is executed in such amanner that it has a section 2 i which extends in the peripheraldirection of the sealing part 2 and, together with the other end 2 h,forms an overlapping ring gap in the peripheral direction. The sealingpart 2 has elastic properties so that it has a clearance C in the regionof the parting joint 2 l. In the preceding exemplary embodiment, thesealing part 2 is executed in such a manner that its radial wallthickness D, beginning at the position Dmax opposite to the partingjoint 2 l, continually decreases towards the parting joint 2l, whichmeans in the direction D1 or D2. As a result, even a sealing partmanufactured of a material with a high modulus of elasticity, such as ahigh temperature polymer, for example, has a behavior towards theparting joint 2 l which is increasingly elastic and/or soft in bending.

FIG. 3 shows a longitudinal section through a dry running sealingarrangement or a so-called packing 6. To this belongs at least onesealing chamber 14 surrounding the piston rod 4, which is formed of twochamber rings 5 and which are screwed sealingly together to form theassociated cylinder space 15. A two-part sealing 10 ring 12 is placed inthe sealing chamber 14 and comprises a sealing part 2 as well as a coverring 1. In addition, a hose spring 13 surrounds the cover ring 1. Thesealing surface 2 a has a surface 2 c diverging in wedge shape towardsthe compression space 15.

The sealing part 2 of FIG. 4 has a sealing surface 2 a with a conicallydiverging partial surface 2 c. The partial surface 2 c is interrupted atthree places by a web 2 p. FIG. 4a shows a section through the sealingpart 2 along the line B—B and shows the cone-shaped partial surface 2 cwhich extends in the axial direction, as well as the cylindricallyextending partial surface 2 b which produces the sealing action betweenthe sealing part 2 and the piston rod 4. The partial surface 2 cextending in a cone shape intersects the surface of the piston rod 4 atan angle β. FIG. 4b shows a section through a web 2 p of the sealingpart 2 along the line C—C. A web 2 p is executed in such a manner thatthe sealing surface 2 a has a height in the axial directioncorresponding to the height H of the sealing part 2 and extends parallelto the surface of the shaft 4. A web 2 p lies in contact with the pistonrod 4 over the entire height H and serves to stabilize the sealing part2. The exemplary embodiment shown has three webs 2 p arranged to bedistributed over the periphery of the surface 2 a, with a web 2 p beingplaced in the region of the parting joint 2 l. A sealing part 2 cannaturally also be executed without a web 2 p so that the conicallydiverging partial surface 2 c extends over the entire periphery of thesurface 2 a without interruption.

The conically diverging partial surface 2 c has a maximum distance Bfrom the shaft 4 in accordance with FIG. 4a. In one embodiment of thesealing part 2, the clearance C is made so wide that it has a width ofthe product of twice the value of π times the distance B. A sealing ring12 with a seating part 2 executed in this manner forms a friction ringin a first phase of operation and a flow ring in a second phase ofoperation. In the first phase of operation, the sealing part 2 has aconically diverging partial surface 2 c. With increasing wear at thecontact surface 2 b, the conically diverging partial surface 2 c isdiminished until the contact surface 2 b extends over the entire heightH. If now the clearance C is made to correspond to a width of theproduct of twice the value of π times the distance B, the clearancebecomes zero as soon as the partial surface 2 c is completely abradedaway. In this state, the sealing part 2 becomes a flow ring because,since the play amounts to zero, hardly any further wear of the contactsurface 2 b results so that the sealing part 2 has an approximatelyconstant leakage during the second phase of operation, or the sealingpart 2 has a maximum flow resistance which remains approximatelyconstant during the second phase of operation.

FIG. 4c shows a side view of the sealing ring of FIG. 4 from thedirection E indicated in FIG. 4. The gap position of the sealing part 2has the two ends 2 h, 2 k, with the end 2 h having the end section 2 iwhich extends in the peripheral direction, so that an overlapping ringgap in the peripheral direction results with a parting joint 21 or aclearance C respectively.

The partial surface 2 c need not be executed to extend divergeconically, but can take on any arbitrary shape in such a manner that aspacing arises in the region of the partial surface 2 c between theshaft 4 and the sealing part 2.

A web 2 p is advantageously placed at each end part 2 k, 2 h, at thering gap 2 l in order to achieve a good sealing action of the sealingring. A plurality of webs 2 p can be distributed along the surface 2 ain the peripheral direction, for example, 2, 4, 7, 12, or 24 webs 2 p.The webs 2 p can be made very narrow in the peripheral direction so thatwith respect to the peripheral direction the distance between two webs 2p is greater or many times greater than the width of the web 2 p. Thewebs 2 p can be executed with a constant width or else have differingwidths.

The sealing part 2 can be made of a plastic such aspolytetrafluoroethylene (PTFE) or of a modified high-temperature polymersuch as poly(ether ether ketone) (PEEK), poly(ether keytone) (PEK),polyimide (PI), poly(phenylene sulphide) (PPS), polybenzimidazole (PBI),or polyamideimide (PAI).

What is claimed is:
 1. A dry running sealing ring for a dry runningpiston rod with a circular cross-section, wherein the sealing ring ismanufactured from a non-metallic material and has a height in an axialdirection and a sealing surface oriented toward a sliding surface;wherein the sealing surface consists of a diverging section thatdiverges from the sliding surface over a first part of the height and acontact section that extends substantially cylindrically over a secondpart of the height and is in contact with the sliding surface; whereinthe sealing surface is arranged such that the diverging section is at ahigh pressure side of the sealing ring and the contact section is at alow pressure of the sealing ring; wherein the sealing ring has a ringgap with a compensatory clearance; wherein the diverging sectiondiverges conically in a radial direction by a maximum distance; andwherein the compensatory clearance has a width equal to the product oftwice the value of π times the maximum distance.
 2. A sealing ring inaccordance with claim 1 wherein the diverging section diverges conicallyfrom the sliding surface.
 3. A sealing ring in accordance with claim 1wherein a plurality of webs is arranged to be distributed along thesealing surface in the peripheral direction.
 4. A sealing ring inaccordance with claim 1 wherein the sealing ring comprises a sealingpart and a closure part, and wherein the sealing part is manufactured ofone of either a plastic or a modified high-temperature polymer.
 5. Asealing ring in accordance with claim 4, wherein the sealing part ismanufactured of polytetrafluoroethylene (i.e., PTFE).
 6. A sealing ringin accordance with claim 4, wherein the sealing part is manufactured ofone of a group of materials consisting of poly (ether ether ketone)(i.e., PEEK), poly (ether ketone) (i.e., PEK), polyimide (i.e., PI),poly (phenylene sulphide) (i.e., PPS), polybenzimidazole (i.e., PBI),and polymideimide (i.e., PAI).
 7. A sealing ring in accordance withclaim 1 wherein the sealing ring comprises a sealing part and a closurepart; and wherein the sealing part has a parting joint and a radial wallthickness decreasing towards the parting joint.
 8. A packing for sealinga dry running piston rod with at least one dry running sealing ringmanufactured from a non-metallic material, wherein each of the at leastone sealing ring has a circular cross section, a height in an axialdirection, and a sealing surface oriented toward a sliding surface;wherein the sealing surface consists of a diverging section thatdiverges from the sliding surface over a first part of the height and acontact section that extends substantially cylindrically over a secondpart of the height and is in contact with the sliding surface; whereinthe sealing surface is arranged so that the diverging section is at ahigh pressure side of the sealing ring and the contact section is at alow pressure side of the sealing ring; wherein the sealing ring has aring gap with a compensatory clearance; wherein the diverging sectiondiverges conically in a radial direction by a maximum distance; andwherein the compensatory clearance has a width equal to the product oftwice the value of π times the maximum distance.
 9. A piston compressorwith at least one dry running sealing ring manufactured from anon-metallic material, wherein each of the at least one sealing ring hasa circular cross section, a height in an axial direction, and a sealingsurface oriented toward a sliding surface; wherein the sealing surfaceconsists of a diverging section that diverges from the sliding surfaceover a first part of the height and a contact section that extendssubstantially cylindrically over a second part of the height and is incontact with the sliding surface; wherein the sealing surface isarranged so that the diverging section is at a high pressure side of thesealing ring and the contact section is at a low pressure side of thesealing ring; wherein the sealing ring has a ring gap with acompensatory clearance; wherein the diverging section diverges conicallyin a radial direction by a maximum distance; and wherein thecompensatory clearance has a width equal to the product of twice thevalue of π times the maximum distance.